Aluminum nitride barrier layer

ABSTRACT

A method of forming features in a dielectric layer is described. A via, trench or a dual-damascene structure may be present in the dielectric layer prior to depositing a conformal aluminum nitride layer. The conformal aluminum nitride layer is configured to serve as a barrier to prevent diffusion across the barrier. The methods of forming the aluminum nitride layer involve the alternating exposure to two precursor treatments (like ALD) to achieve high conformality. The high conformality of the aluminum nitride barrier layer enables the thickness to be reduced and the effective conductivity of the subsequent gapfill metal layer to be increased.

FIELD

Embodiments disclosed herein relate to forming damascene structures formicroelectronic devices.

BACKGROUND

Low-k dielectrics are those having a smaller dielectric constant thansilicon dioxide (SiO₂). Silicon dioxide has a dielectric constant of3.9. Low-k dielectric materials are positioned between conductingelements in integrated circuits to improve achievable switching speedand reduce power consumption as feature sizes are decreased. Low-kdielectric films are achieved by selecting film materials which reducedielectric constant and/or inserting pores inside the film.

Besides decreasing the dielectric constant, the conductivity of theconducting elements (e.g. metal lines) can be increased. As aconsequence, copper has replaced many other metals for longer lines(interconnects). Copper has a lower resistivity and higher currentcarrying capacity. However, precautions must be taken to discouragediffusion of copper into surrounding materials. Besides the need toinhibit diffusion into active semiconductor areas, copper should be keptfrom entering porous low-k dielectric regions to avoid shorting andmaintain the low dielectric constant.

An example of an integrated circuit structure which implements copper asan interconnect material is a dual-damascene structure. In adual-damascene structure, the dielectric layer is etched to define boththe contacts/vias and the interconnect lines. Metal is inlaid into thedefined pattern and any excess metal is removed from the top of thestructure in a planarization process, such as chemical mechanicalpolishing (CMP).

Novel liner layers and/or process modifications are needed to achievehigh conductivity for the interconnect connections in combination with alow-k for the dielectric material.

SUMMARY

A method of forming features in a dielectric layer is described. A via,trench or a dual-damascene structure may be present in the dielectriclayer prior to depositing a conformal aluminum nitride layer. Theconformal aluminum nitride layer is configured to serve as a barrier toprevent diffusion across the barrier. The methods of forming thealuminum nitride layer involve the alternating exposure to two precursortreatments (like ALD) to achieve high conformality. The highconformality of the aluminum nitride barrier layer enables the thicknessto be reduced and the effective conductivity of the subsequent gapfillmetal layer to be increased.

Embodiments disclosed herein include methods of forming a gap in a low-kdielectric layer. The methods include forming a conformal barrier layeron a patterned substrate. The patterned substrate comprises a gap abovean underlying copper layer. Sidewalls of the gap include low-kdielectric material. The conformal barrier layer is formed by exposingthe patterned substrate to an aluminum-containing precursor and thenexposing the patterned substrate to a nitrogen-and-hydrogen-containingprecursor while concurrently exposing the patterned substrate toultraviolet light. The methods further include depositing a conductorinto the gap.

Embodiments disclosed herein include methods of forming a conformalaluminum nitride layer. The methods include forming a conformal aluminumnitride layer on a patterned substrate placed in a substrate processingregion by: i) flowing an organoaluminum precursor into the substrateprocessing region; ii) removing process effluents from substrateprocessing region; iii) flowing a nitrogen-and-hydrogen-containingprecursor into the substrate processing region while shining ultravioletlight onto the patterned substrate; and (iv) removing process effluentsfrom the substrate processing region.

Operations i), ii), iii) and iv) may occur in the recited order. Theconformal aluminum nitride layer may be configured to prevent diffusionof copper across the conformal aluminum nitride layer. Operations i),ii), iii) and iv) are repeated an integral number of times to form aconformal aluminum nitride layer. The methods may further include anoperation of depositing gapfill metal into the via and the trenchfollowing the last instance of operation iv).

Embodiments disclosed herein include methods of forming a dual-damascenestructure. The methods include forming a conformal silicon carbonnitride layer over a patterned substrate. The patterned substrateincludes a trench and a via below the trench. The via is above anunderlying copper layer. Sidewalls of the trench and the via compriselow-k dielectric walls. The trench is fluidly coupled to the via and theconformal silicon carbon nitride layer forms a hermetic seal between thetrench and the low-k dielectric walls. The methods further includeselectively removing a bottom portion of the conformal silicon carbonnitride layer from the underlying copper layer while retaining a sideportion of the conformal silicon carbon nitride layer on the low-kdielectric walls. The methods further include placing the patternedsubstrate in a substrate processing region, and i) flowing analuminum-containing precursor into the substrate processing region, ii)removing process effluents from substrate processing region, iii)flowing a nitrogen-and-hydrogen-containing precursor into the substrateprocessing region while shining ultraviolet light onto thedual-damascene structure of the patterned substrate, and iv) removingprocess effluents from the substrate processing region.

Additional embodiments and features are set forth in part in thedescription that follows, and in part will become apparent to thoseskilled in the art upon examination of the specification or may belearned by the practice of the disclosed embodiments. The features andadvantages of the disclosed embodiments may be realized and attained bymeans of the instrumentalities, combinations, and methods described inthe specification.

DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the embodimentsmay be realized by reference to the remaining portions of thespecification and the drawings.

FIG. 1 is a flow chart of a conformal aluminum nitride formation processaccording to embodiments.

FIGS. 2A, 2B, 2C and 2D show cross-sectional views of a device at stagesof a conformal aluminum nitride formation process according toembodiments.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION

A method of forming features in a dielectric layer is described. A via,trench or a dual-damascene structure may be present in the dielectriclayer prior to depositing a conformal aluminum nitride layer. Theconformal aluminum nitride layer is configured to serve as a barrier toprevent diffusion across the barrier. The methods of forming thealuminum nitride layer involve the alternating exposure to two precursortreatments (like ALD) to achieve high conformality. The highconformality of the aluminum nitride barrier layer enables the thicknessto be reduced and the effective conductivity of the subsequent gapfillmetal layer to be increased.

Copper damascene and dual-damascene structures have been used forseveral decades and involve depositing copper into gaps in a patternedlow-k dielectric layer. Dual-damascene structures include two distinctpatterns formed into a dielectric layer. The lower pattern may includevia structures whereas the upper pattern may include a trench. The viaand the trench are filled at the same time which is the operation forwhich the dual-damascene process gets its name. The dielectric constantof the low-k dielectric layer may be undesirably increased duringsubsequent processing so a conformal hermetic layer may be depositedcovering both the patterned low-k dielectric layer and the exposedunderlying copper layer. The portion of the conformal hermetic layercovering the underlying copper layer may be removed while retaining theconformal hermetic layer covering the patterned low-k dielectric layer.This selective removal improves electrical contact between gapfill metaland the underlying metal layer.

The methods described herein have been developed to form conformalaluminum nitride over the patterned structure to discourage diffusionand reduce the associated degradation of the low-k dielectric layer andother portions of the device under manufacture. The methods describedherein provide the benefit of increasing conductivity and performance ofcompleted devices. The conductivity is increased by reducing thethickness of the conformal aluminum nitride layer compared to pastdeposition methods. The reduced thickness enables more gapfill metal(e.g. gapfill copper or gapfill tungsten) to be deposited in a givendimension of via and trench. An additional benefit is the an improvementin barrier capabilities which may, for example, maintain a lowerdielectric constant in the low-k dielectric layer. Maintaining a lowdielectric constant in the low-k dielectric layer improves performanceof completed devices (e.g. higher switching speeds or lower powerconsumption).

In order to better understand and appreciate the embodiments disclosedherein, reference is now made to FIG. 1 which is a conformal aluminumnitride formation process 101 according to embodiments. Concurrently,reference will be made to FIGS. 2A, 2B, 2C and 2D which showcross-sectional views of a device at various stages of conformalaluminum nitride formation process 101. The portion of the device shownmay be a back-end of the line (BEOL) interconnect portion of anintegrated circuit during formation in embodiments. Prior to the firstoperation (FIG. 2A), an exposed titanium nitride layer is formed,patterned into titanium nitride hardmask 230, and used to pattern anunderlying low-k dielectric layer 220 on the patterned substrate. Acopper barrier dielectric layer 210 may be used to physically separateunderlying copper layer 201 from low-k dielectric layer 220. Underlyingcopper layer 201 is located beneath the low-k dielectric layer and isexposed to the atmosphere through the combination of the via and thetrench. Generally speaking, underlying copper layer 201 may be anunderlying metal layer.

Low-k dielectric layer 220 may have pores within the film to achieve alower dielectric constant than silicon oxide. Low-k dielectric layer 220may comprise or consist of silicon, carbon and oxygen, in embodiments,to further reduce the dielectric constant below that of silicon oxide.Low-k dielectric layer 220 may therefore be referred to as siliconoxycarbide.

Conformal aluminum nitride formation process 101 has been developed toachieve and maintain a low dielectric constant within low-k dielectriclayer 220 during processing and during the active life of the integratedcircuit ultimately produced.

Titanium nitride hardmask 230 may be physically separated from low-kdielectric layer 220 by an auxiliary hardmask to facilitate processing,though no such layer is shown in FIGS. 2A, 2B, 2C or 2D. The auxiliaryhardmask layer may be a silicon oxide hardmask in embodiments. “Top”,“above” and “up” will be used herein to describe portions/directionsperpendicularly distal from the substrate plane and further away fromthe center of mass of the substrate in the perpendicular direction.“Vertical” will be used to describe items aligned in the “up” directiontowards the “top”. Other similar terms may be used whose meanings willnow be clear.

A conformal hermetic layer 240-1 is formed on the patterned substrate inoperation 110, shown following formation in FIG. 2A. The conformalhermetic layer is conformal over the features of the patterned substrateand contacts underlying copper layer 201 directly in embodiments. Theconformal hermetic layer may also contact low-k dielectric layer 220directly according to embodiments. Conformal hermetic layer 240-1 may bea silicon-and-carbon-containing layer or a silicon carbon nitride layerin embodiments. Conformal hermetic layer 240-1 may comprise or consistof silicon, carbon and nitrogen, according to embodiments, and may bereferred to as silicon carbon nitride or Si—C—N. Conformal hermeticlayer 240-1 may inhibit diffusion of subsequently-introduced etchants ormoisture and may therefore protect the integrity of low-k dielectriclayer 220 during and after processing in embodiments. The depositionprocess of conformal hermetic layer 240-1 may result in a lowering ofthe dielectric constant simply from the displacement of absorbates andother components within low-k dielectric layer 220. Conformal hermeticlayer 240-1 (and conformal hermetic layer 240-2 later) may help to avoiddiffusion of copper into low-k dielectric layer 220 as well, accordingto embodiments.

Conformal hermetic layer (e.g. Si—C—N) is exposed to acetic acid inoperation to etch back and expose underlying copper layer 201 inoperation 120, shown following the operation in FIG. 2B. More generally,a mild acid may be used instead of or to augment the acetic acidaccording to embodiments. The mild acid may be referred to as a weakacid and may have a pH between 5 and 7 in embodiments. Selective etchingoperation 120 may involve liquid or gas-phase etchants according toembodiments. A process which uses gas-phase etchants may be referred toherein as a dry-etch and etching operations within a dry-etch may bereferred to as dry-etching conformal hermetic layer 240-1. Afterselective etching operation 120 a portion of conformal hermetic layer240-1 remains and will be referred to as conformal hermetic layer 240-2as shown in FIG. 2B. Conformal hermetic layer 240-2 may also be referredto as the remaining portion of conformal hermetic layer 240-1. Conformalhermetic layer 240-2 continues to seal low-k dielectric layer 220 fromenvironmental influences such as subsequently introduced reactants ormoisture which may get into pores in low-k dielectric layer 220 andundesirably increase the dielectric constant.

A conformal aluminum nitride layer 250 is now formed on conformalhermetic layer 240-2 and underlying copper layer 201 using analternating exposure technique to form an extremely conformal film.Conformal aluminum nitride layer 250 may consist of aluminum andnitrogen according to embodiments. The patterned substrate istransferred into a substrate processing region in the event that thepatterned substrate is not already present in the substrate processingregion. An aluminum-containing precursor is flowed into the substrateprocessing region in operation 130. The aluminum-containing precursormay be an organometallic precursor or an organoaluminum precursoraccording to embodiments. The aluminum-containing precursor may compriseor consist of one or more of triethylaluminum or trimethylaluminum. Thealuminum-containing precursor may comprise or consist of aluminum,carbon and hydrogen in embodiments. Following exposure, processeffluents (such as unused precursor and reaction by-products) areremoved from the substrate processing region in operation 140.

In operation 150, the substrate is exposed to anitrogen-and-hydrogen-containing precursor and irradiated withultraviolet light at the same time. The nitrogen-and-hydrogen-containingprecursor may be flowed into the substrate processing region, inoperation 150, to expose the substrate to the precursor in embodiments.The nitrogen-and-hydrogen-containing precursor may comprise or consistof NH₃, N₂H₂, N₂H₄ according to embodiments. The nitrogen-and-hydrogen-containing precursor may be NxHy where x and y are integersin embodiments. The nitrogen-and-hydrogen-containing precursor maycomprise or consist of nitrogen and hydrogen in embodiments. Operation150 completes one growth cycle of conformal aluminum nitride layer 250according to embodiments in embodiments. Process effluents may beremoved in operation 160 either in preparation for depositing aconductor or repeating operations 130-150 and forming a thickerconformal aluminum nitride layer 250.

In operation 170, the thickness of conformal aluminum nitride layer 250is determined to either be sufficient or to require another iteration ofoperations 130-150 to form another layer of aluminum nitride. Operation170 may be a direct measurement of conformal aluminum nitride layer 250or operation 170 may be a comparison of the number of cycles completedwith a stored target number of cycles. Should the target thickness ortarget number of cycles have been achieved, conformal aluminum nitridelayer 250 is finished as shown in FIG. 2C. Conformal aluminum nitrideformation process 101 then includes formation of gapfill metal (e.g.gapfill copper 260) into the via and trench of the dual-damascenestructure of the patterned substrate in operation 140. The devicefollowing operation 140 is shown in FIG. 2D. FIG. 2D shows underlyingcopper 201 electrically connected to gapfill copper 260 throughconformal aluminum nitride layer 250. As a result of operation 120,there is no or substantially no portion of conformal hermetic layer 240to negatively impact the conductivity from underlying copper 201 togapfill copper 260. Technically, FIG. 2D shows gapfill copper 260 aftera planarizing chemical mechanical polishing (CMP) operation since thetop surface is flush with the low-k dielectric film stack. Conformalnitride formation process 101 further includes an operation of chemicalmechanical polishing the gapfill metal layer according to embodiments.

The thickness of conformal aluminum nitride layer 250 should besufficient to form a barrier to diffusion between regions above andbelow the conformal aluminum nitride layer. In embodiments, thethickness of conformal aluminum nitride layer 250 is sufficient to stopdiffusion of, for example, metal atoms into dielectrics orsemiconductors in the vicinity. The thickness should be less than athreshold amount to enable enough conducting material (e.g. copper) todesirably fill the gaps in the patterned low-k dielectric layer and formconducting contacts. Conformal aluminum nitride layer 250 may reside onunderlying copper layer 201 and on conformal hermetic layer 240following deposition. If no conformal hermetic layer 240 is used, thenconformal aluminum nitride layer 250 may reside on underlying copperlayer 201 and directly on low-k dielectric layer 220 in embodiments. Thethickness of the conformal aluminum nitride layer 250 may be less than 6nm, less than 4 nm, between 1 nm and 6 nm, between 1.5 nm and 5 nm, orbetween 2 nm and 4 nm according to embodiments. Conformal aluminum oxidelayer 250 may be formed on wall of a gap in the patterned low-kdielectric layer according to embodiments.

The thickness of conformal hermetic layer 240 should be sufficient toform a hermetic seal configured to keep moisture out of the low-kdielectric layer. The thickness should be less than a threshold amountto enable enough conducting material (e.g. copper) to desirably fill thegaps in the patterned low-k dielectric layer and form conductingcontacts. The thickness should also be less than a threshold amount toensure the portion of the conformal hermetic layer on the underlyingcopper layer is selectively removable. A first portion of the conformalhermetic layer resides on the underlying copper layer followingdeposition. A second portion of the conformal hermetic layer resides onthe low-k dielectric layer 220, for example on wall of a gap in thepatterned low-k dielectric layer following deposition. The thickness ofthe second portion of the conformal hermetic layer may be greater than1.5 nm or greater than 2 nm, according to embodiments, after depositionbut before selective removal. The thickness of the second portion of theconformal hermetic layer may be less than 30 nm or less than 40 nm, inembodiments, after deposition but before selective removal.

The dielectric constant of low-k dielectric layer 220 may be between 2.4and 2.9 prior to depositing the (optional) conformal hermetic layer andthe conformal aluminum nitride layer. The conformal hermetic layer maybe deposited by UV-assisted chemical vapor deposition (UV-CVD) and thedeposition process may result in a reduction of the dielectric constant,possibly by replacing hydroxyl groups on the interior surfaces of poreswith methyl groups. The dielectric constant may be reduced by 0.1 simplyby depositing conformal hermetic layer 240-1. The dielectric constantmay be between 2.3 and 2.8 after deposition but before selectiveremoval.

The selective removal operation may remove the first portion but not thesecond portion of the conformal hermetic layer. The selective removaloperation may expose the underlying copper layer in embodiments. Thisensures subsequent capability of achieving a highly conductiveconnection between the conductor which fills the gaps in the patternedlow-k dielectric layer and the underlying copper layer (or, moregenerally, another underlying metal layer). The contact between thegapfill conductor and the underlying copper layer may be an ohmiccontact according to embodiments. The thickness of the second portion ofthe conformal hermetic layer may be greater than 1.5 nm, or greater than2 nm, according to embodiments, after the selective removal operation.The thickness of the second portion of the conformal hermetic layer maybe less than 3 nm or less than 4 nm, in embodiments, after the selectiveremoval operation. After the selective removal operation, the dielectricconstant of low-k dielectric layer 220 may be between 2.3 and 2.8. Insome embodiments, no conformal hermetic layer is present, in which caseall the thicknesses are zero and operations 110 and 120 are not presentin the method. The dielectric constant of low-k dielectric layer 220 maybe between 2.3 and 2.8 following formation of conformal aluminum nitridelayer 250, after depositing gapfill copper/metal 260 or as measured in acompleted device in embodiments.

The trench and/or via structures lined with the conformal hermetic layermay be a dual-damascene structure including a via underlying a trench.The via may be a low aspect ratio gap and may be, e.g., circular asviewed from above the patterned substrate laying flat. The structure maybe at the back end of the line which may result in larger dimensionsdepending on the device type. A width of the via may be less than 50 nm,less than 40 nm, less than 30 nm or less than 20 nm according toembodiments. A width of the trench may be less than 70 nm, less than 50nm, less than 40 nm or less than 30 nm in embodiments. The dimensionsdescribed herein apply to structures involving a single-patterned low-kdielectric layer or a multi-patterned low-k dielectric layer (e.g.dual-damascene structure). An aspect ratio of the via may be about 1:1,as viewed from above, whereas an aspect ratio of the trench may begreater than 10:1 since the trench is used to contain a conductor meantto electrically attach multiple vias.

The examples described herein involve the preparation of a long trenchabove a low-aspect ratio via in a dual-damascene structure. Generallyspeaking the structure may involve only one level and the low-kdielectric layer may have long trenches and/or vias according toembodiments. For the purposes of description herein and claimrecitations below, a via is simply a low-aspect ratio gap and so theterm “gap” covers all holes in a low-k dielectric described herein.Generally speaking, underlying copper layer 201 may be any underlyingconducting layer in embodiments.

During operations 130 and/or 150, the substrate may be maintainedbetween 30° C. and about 500° C. in general. The temperature of thepatterned substrate during operations 130 and/or 150 may be between 100°C. and 450° C., between 150° C. and 400° C. or between 200° C. and 370°C. in embodiments. During etching operation 120, the substrate may bemaintained between −30° C. and about 200° C. in general. The temperatureof the patterned substrate during operation 120 may be between −20° C.and 150° C., 10° C. and 200° C., between 20° C. and 75° C. or between25° C. and 50° C. in embodiments.

As used herein “substrate” may be a support substrate with or withoutlayers formed thereon. The patterned substrate may be an insulator or asemiconductor of a variety of doping concentrations and profiles andmay, for example, be a semiconductor substrate of the type used in themanufacture of integrated circuits. Exposed “silicon oxide” of thepatterned substrate is predominantly SiO₂ but may include concentrationsof other elemental constituents such as, e.g., nitrogen, hydrogen andcarbon. In some embodiments, silicon oxide portions etched using themethods disclosed herein consist essentially of silicon and oxygen.Exposed “silicon nitride” of the patterned substrate is predominantlySi₃N₄ but may include concentrations of other elemental constituentssuch as, e.g., oxygen, hydrogen and carbon. In some embodiments, siliconnitride portions described herein consist essentially of silicon andnitrogen. Exposed “titanium nitride” of the patterned substrate ispredominantly titanium and nitrogen but may include concentrations ofother elemental constituents such as, e.g., oxygen, hydrogen and carbon.In some embodiments, titanium nitride portions described herein consistessentially of titanium and nitrogen. Exposed “aluminum nitride” of thepatterned substrate is predominantly aluminum and nitrogen but mayinclude concentrations of other elemental constituents such as, e.g.,oxygen, hydrogen and carbon. In some embodiments, aluminum nitrideportions described herein consist essentially of aluminum and nitrogen.The low-k dielectric may be “silicon oxycarbide” which is predominantlysilicon, oxygen and carbon but may include concentrations of otherelemental constituents such as, e.g., nitrogen and hydrogen. In someembodiments, silicon oxycarbide portions described herein consistessentially of silicon, oxygen and carbon. Exposed “silicon carbonnitride” of the patterned substrate is predominantly silicon, carbon andnitrogen but may include concentrations of other elemental constituentssuch as, e.g., oxygen and hydrogen. In some embodiments, silicon carbonnitride portions described herein consist essentially of silicon, carbonand nitrogen. “Copper” of the patterned substrate is predominantlycopper but may include concentrations of other elemental constituentssuch as, e.g., oxygen, nitrogen, hydrogen and carbon. In someembodiments, copper portions described herein consist essentially ofcopper. Analogous definitions for other metals will be understood fromthis copper definition.

The term “gap” is used throughout with no implication that the etchedgeometry has a large horizontal aspect ratio. Viewed from above thesurface, gaps may appear circular, oval, polygonal, rectangular, or avariety of other shapes. The term “trench” is defined as a large aspectratio gap with a long dimension (viewed from above) at least ten times ashort dimension (also viewed from above). The long dimension does nothave to be linear, e.g., a trench may be in the shape of a moat aroundan island of material, in which case the long dimension is thecircumference. The term “via” is used to refer to a low aspect ratio gapwhich may or may not be filled with metal to form a vertical electricalconnection. As used herein, a conformal layer or conformal etch processrefers to a generally uniform removal of material on a surface in thesame shape as the surface, i.e., the surface of the etched layer and thepre-etch surface are generally parallel. A person having ordinary skillin the art will recognize that the etched interface likely cannot be100% conformal and thus the term “generally” allows for acceptabletolerances.

Having disclosed several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of thedisclosed embodiments. Additionally, a number of well-known processesand elements have not been described in order to avoid unnecessarilyobscuring the embodiments. Accordingly, the above description should notbe taken as limiting the scope of the claimed subject matter.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neitheror both limits are included in the smaller ranges is also encompassedwithin the disclosure, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a process” includes aplurality of such processes and reference to “the dielectric material”includes reference to one or more dielectric materials and equivalentsthereof known to those skilled in the art, and so forth.

Also, the words “comprise,” “comprising,” “include,” “including,” and“includes” when used in this specification and in the following claimsare intended to specify the presence of stated features, integers,components, or steps, but they do not preclude the presence or additionof one or more other features, integers, components, steps, acts, orgroups.

1. A method of forming a gap in a low-k dielectric layer, the methodcomprising: forming a conformal barrier layer on a patterned substrate,wherein the patterned substrate comprises a gap above an underlyingcopper layer, wherein sidewalls of the gap comprise low-k dielectricmaterial, wherein the conformal barrier layer is formed by: exposing thepatterned substrate to an aluminum-containing precursor and then,exposing the patterned substrate to a nitrogen-and-hydrogen-containingprecursor while concurrently exposing the patterned substrate toultraviolet light; and depositing a conductor into the gap.
 2. Themethod of claim 1 wherein the aluminum-containing precursor is anorganometallic precursor.
 3. The method of claim 1 wherein thealuminum-containing precursor comprises comprise one or more oftriethylaluminum or trimethylaluminum.
 4. The method of claim 1 whereina width of the gap is less than 20 nm.
 5. The method of claim 1 whereina dielectric constant of the low-k dielectric material is between 2.3and 2.8 following formation of the conformal barrier layer.
 6. A methodof forming a conformal aluminum nitride layer, the method comprising:forming a conformal aluminum nitride layer on a patterned substrateplaced in a substrate processing region by: i) flowing an organoaluminumprecursor into the substrate processing region; ii) removing processeffluents from substrate processing region; iii) flowing anitrogen-and-hydrogen-containing precursor into the substrate processingregion while shining ultraviolet light onto the patterned substrate; and(iv) removing process effluents from the substrate processing region. 7.The method of claim 6 wherein operations i) through iv) occur in therecited order.
 8. The method of claim 6 wherein the conformal aluminumnitride layer is configured to prevent diffusion of copper across theconformal aluminum nitride layer.
 9. The method of claim 6 wherein theconformal aluminum nitride layer consists of aluminum and nitrogen. 10.The method of claim 6 wherein operations i) through iv) are repeated anintegral number of times to form a conformal aluminum nitride layer. 11.The method of claim 10 wherein a thickness of the conformal aluminumnitride layer is less than 6 nm.
 12. The method of claim 6 furthercomprising an operation of depositing gapfill metal into the via and thetrench following operation iv).
 13. A method of forming a dual-damascenestructure, the method comprising: forming a conformal silicon carbonnitride layer over a patterned substrate, wherein the patternedsubstrate comprises a trench and a via below the trench, wherein the viais above an underlying copper layer, wherein sidewalls of the trench andthe via comprise low-k dielectric walls, and wherein the trench isfluidly coupled to the via and the conformal silicon carbon nitridelayer forms a hermetic seal between the trench and the low-k dielectricwalls; selectively removing a bottom portion of the conformal siliconcarbon nitride layer from the underlying copper layer while retaining aside portion of the conformal silicon carbon nitride layer on the low-kdielectric walls; placing the patterned substrate in a substrateprocessing region; i) flowing an aluminum-containing precursor into thesubstrate processing region ii) removing process effluents fromsubstrate processing region; iii) flowing anitrogen-and-hydrogen-containing precursor into the substrate processingregion while shining ultraviolet light onto the dual-damascene structureof the patterned substrate; and iv) removing process effluents from thesubstrate processing region.
 14. The method of claim 13 wherein theoperation of selectively removing the conformal silicon carbon nitridelayer comprises dry-etching the conformal silicon carbon nitride layer.15. The method of claim 13 wherein a width of the trench is less than 70nm.